Listing 1: Encrypting a password

/*****************************************************************************
*                             Listing 1                                     *
*****************************************************************************/

#include        <stdio.h>
#include        <sys/types.h>
#include        <limits.h>

extern char *getpass ();
extern char *crypt ();

/*
* The salt is a two character string chosen from the set [a-zA-Z0-9./]
*/
static char alphabet [] =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789./";

int
make_passwd (passwd, encrypted)
char *passwd;
char *encrypted;
{
char *cp;
char salt [3];
int  random;
unsigned int seed;
time_t t;

/*
* To generate a random "salt", we first pick a
* "seed" to set a random starting point.
*/
time (&t);
seed  = (unsigned int) (t % INT_MAX);
srand (seed);

/*
* Pick two random characters from the salt alphabet
*/
random = ((rand ()) >> 4) % 64;
salt [0] = alphabet [random];

random = ((rand ()) >> 4) % 64;
salt [1] = alphabet [random];

salt [2] = '\0';

/*
* Encrypt the password
*/
cp = crypt (passwd, salt);

/*
* Store the encrypted string in
* the given argument.
*/
strcpy (encrypted, cp);

return 0;

}